This invention relates to an image input device for obtaining high resolution image signals from an image source.
Solid light sensors, which developed quickly after charge coupled devices became available, have recently been used as multi-element devices for obtaining high resolution images. Since it is difficult to make multi-element devices of solid light sensors, a recent experiment was made to obtain a one dimensional image having high resolution by using a two dimensional sensor. The experiment is described in an article entitled "High Resolution Image Line Scanning With an Area Image Sensor" by Robert A. Sprague and William D. Turner, 1978 Proceedings of the International Conference on the Application of Charged Coupled Devices, pp 1-13 to 1-23, Oct. 25-27, 1978, held in San Diego, Calif. An illustration of this experiment is shown in FIGS. 1A and 1B. An image light generated from an image source 1 such as an illuminated document is focused onto a mask 2 and a two dimensional sensor 3 through lenses 4, 5 and 6. The two dimensional sensor 3 converts the image light into electrical image signals. As shown in FIG. 1B, mask 2 has many rectangular apertures 7 in a two-dimensional array. Apertures in adjacent rows, for example, rows 7A and 7B, are staggered at a predetermined resolution. Each aperture corresponds to a photoelectric converting element of sensor 3.
If image source 1 is moved in the direction of arrow 8 in FIG. 1A, the image light generated from line L of image source 1 irradiates aperature rows 7A, 7B, 7C . . . 7E in order. Then the movement of moving image source 1 is synchronized with the reading out of the electrical signals from the rows of photoelectric converting elements corresponding to aperture rows 7A, 7B . . . 7E. In other words, the image source 1 is moved in a predetermined timed order corresponding to the reading out of electrical signals from the photoelectric converting elements. The electrical signals are in a memory to form one dimensional image signals having high resolution.
The above method requires precision and an expensive mechanism because it is necessary to synchronize the movement of image source 1 at a precision higher than the desired resolution. Also, although this method uses a two dimensional sensor 3, the sensor produces only a one dimensional image.
Another method for obtaining high resolution image signals is described in Japanese Pat. No. 53-101939. In this method, an image is obtained by vibrating a two dimensional image sensor array relative to an image source in at least two directions of the plane containing the array. In this patent disclosure, the image sensor array is vibrated by an electro magnet. Also, the mirrors or lenses of the optical system can be vibrated by the electro magnet. A disadvantage of this method is that it is difficult to control the relative position between the sensor array and the image source due to the vibration. Thus, it is difficult to obtain high resolution image signals.